I haven't done anything like this, but working from "first principles" I guess that something like the following would work. I assume that you know a bit about fermenting etc, but I would do a small test batch along the following lines then scale it up if it works.
1. Make up a white sugar and water mix to get as SG of 1.060. If you don't have a hydrometer, buy one. As a guide, plug some numbers into the "Vinolab" calculator (just Google Vinolab) which says that 156 grams of sugar per litre should give you a SG of 1.060 or a potential 8% ABV. This pretty much lines up with my experience where a concentration of 200g/L gave about 10% ABV.
2. Think about adding Campden tablets (metabisulphite or SO2) and leave for 24 hours before fermenting or boil the sugar and water mix to get rid of any "bugs".
3. Ferment this under air lock with a "robust" yeast like EC1118 (plus a similar amount of nutrient like DAP), although I imagine that any yeast that goes down to 1.000 will do. The rate is 1 -2 teaspoons per gallon so a packet should do around 5 gallons or 20 litres.
4. Assuming that you want something like 2.5 volumes of CO2 carbonation (normal beer or soda carbonation), then bottle when the SG has dropped to around 1.005 or 1.006. you will need a hydrometer to know when this is reached (or you could try bottling some of your "test batch" in a couple of plastic (not glass) soda bottles at say, two weeks and four weeks after starting fermentation then "guestimate" what fermentation time might be about right for bottling. The "right" bottle should end up as firm as a normal soda bottle.
5. If this seems a bit scary in terms of potential exploding bottles, then let it ferment down for a month or so until the SG is stable at 1.000 or a bit below, or you have gone for a while with no bubbles rising. Then add about 15g of sugar per litre and bottle. This sugar will ferment and generate around 2.5-3.0 volumes of CO2 (and also add a bit less than 1% ABV, so if you go this way, knock the initial sugar back to 140g/L).
Others may well have different ideas but at least this might give you something to start with. The "kegging people" will no doubt recommend just fermenting it all the way down then carbonate in a keg and bottle. This is certainly the easy way if you have a kegging setup.
